The Osa Peninsula, often eclipsed by Corcovado's fame, offers a less trodden but equally thrilling landscape where waterfalls and rivers shape raw adventure. Here, trails challenge hikers with steep climbs, slippery rocks, and sudden river crossings, demanding respect for a wilderness relentlessly alive. Start early to catch the morning light filtering through broad-leaved canopies, while the rivers ahead dare you forward with their rushing currents.

One standout route is the Agua Blanca Waterfall trek. A roughly 8 km round trip, it gains about 300 meters in elevation, weaving alongside an ever-present stream that murmurs promises of cool respite. The path combines uneven forest floor and rocky slabs slick with perpetual mist. Expect 3 to 4 hours of steady hiking, punctuated by brief pauses to spot darting kingfishers or a sudden splash from a river otter slipping beneath the surface.

Another rewarding option is the Tigre River hike. Covering 10 km with moderate elevation, the terrain here feels more rugged—slopes fall sharply on one side, while roots grab at your boots, demanding focus with every step. The Tigre's pools and plunges embody the relentless spirit of the wild, coaxing you to test your balance along river stones or dip your hands in water alive with cool currents. Early afternoons bring a chance to witness caimans basking silently, as the forest breathes heavy and humid.

Practical preparation is key. Waterproof boots with good grip are non-negotiable; the trails alternately sponge moist earth or stone that gleams dangerously when wet. Hydration is critical—carry at least 2 liters of water and a lightweight filtration system for topping off using river sources. Plan your trek for the dry season (December to April) to avoid flash floods and muddy paths, but know the forest's pulse still beats strong through sporadic rains. Sun protection plus insect repellent keep irritation and sunburn at bay.

Beyond the physical, these treks engage with nature fiercely. You are walking in an ecosystem that commands pace and attention—every splash, every birdcall, every shifting shadow holds importance. Rather than dominating the path, you move alongside a force that demands humility. And the reward? Not just waterfalls and crystal pools, but moments of clear connection where the Osa's rivers and forests speak with edge and mystery.

Whether you’re seasoned or stepping into jungle trekking for the first time, these routes beyond Corcovado offer unmatched adventure. Embrace the challenge with respect, prepare with care, and let the rivers dare you onward.